The Foucault Wikipedia article has always been a hotmess of his mutually incompatible biographers' approaches. I'm pretty sure the sentence you're looking for was what currently stands as

Embracing the Parisian avant-garde, Foucault entered into a romantic relationship with the serialist composer Jean Barraqué. Together, they tried to produce their greatest work; heavily used recreational drugs and engaged in sado-masochistic sexual activity

But continuing with the hotmess theme, it cites three biographies at once for a single clause! You could try look at archived versions of the page to see when it was first added if you really want to chase it down.